#include <iostream>
using namespace std;

int main(){
	int i = 1;
	int sum = 0;
	int index = 1;
	while(i < 39){
		while(index > 0){
			sum++;
			index--;
		}
		i++;
		index = i;
	}
	sum += 20;
	cout<<sum<<endl;
	system("pause");
	return 0;
} 
